This invention relates to semiconductor devices. More particularly, it is concerned with junction field effect transistors of the static induction type and to methods of fabricating.
The static induction transistor is a field effect semiconductor device capable of operation at relatively high frequency and power. The transistors are characterized by a short, high resistivity semiconductor channel region which may be controllably depleted of carriers. The current-voltage characteristics of the static induction transistor are generally similar to those of a vacuum tube triode.
The static induction transistor generally uses vertical geometry with source and drain electrodes placed on opposite sides of a thin, high resistivity layer of silicon of one conductivity type. Gate regions of the opposite conductivity type are positioned in the high resistivity layer on opposite sides of the source. During operation a reverse bias is applied between the gate regions and the remainder of the high resistivity layer causing a depletion region to extend into the channel region below the source. As the magnitude of the reverse bias is varied the source-drain current and voltage derived from an attached energy source will also vary.
Metallic members are formed in ohmic contact with the silicon at the source, gate, and drain regions of the device. These contact members may be fabricated by using any of various well-known conventional metallization techniques. Although current procedures of forming ohmic contacts provide high quality devices further reduction in contact resistance is desirable in order to provide improved device performance.